For a liquid crystal display (LCD) or an organic light-emitting diode (OLED) display, each pixel is driven by a thin film transistor (TFT) arranged behind the pixel, so as to display screen information at a high speed, a high brightness and a high contrast. In the related art, the TFT is usually manufactured by poly silicon (poly-Si) or amorphous silicon (a-Si). The poly-Si has a carrier mobility of 10-200 cm2/V, which is obviously greater than a carrier mobility (1 cm2/V) of the a-Si, so the poly-Si has higher capacitive and storage properties than the a-Si. For the LCD and the OLED display, the TFT is generally formed on a glass substrate. Due to thermodynamic limitations of glass, a crystalline characteristic of the poly-Si TFT and an annealing procedure after ion implantation may not recover effectively. In the case of a reversed bias voltage, a relatively large drain current may occur, and thereby the normal operation of the TFT will be adversely affected.
In order to suppress the drain current of the TFT, usually a lightly-doped region and a heavily-doped region are arranged on a source electrode and a drain electrode of the TFT respectively. A voltage may be partially applied to the lightly-doped region, so a part of the drain current may be cancelled out.
Currently, for the LCD, usually an additional ion implantation process is provided. In other words, after a gate metal layer has been etched, a lightly-doping procedure is performed at first using a gate electrode, and then a heavily-doping procedure is performed through an additional masking process using an image-reversal photoresist (PR) as a mask plate. It is found that, at least two ion implantation processes are required during the manufacture. However, the ion implantation process is time-consuming and expensive, and as a result, the mass production of the array substrate will be adversely affected.